Usin
your Pro
rammable Power Supply 5 - 13
5.5.3 Constant volta
e or constant current source
Your power supply has been desi
ned accordin
to the automatic crossover
principle. This means that each output channel will operate in the Constant
Volta
e (CV) mode or in the Constant Current CC mode, dependin
on:
• the pro
rammed output volta
e V
set
and current I
set
• the resistance (impedance) of the load R
load
, connected to the output channel
For a
iven V
set
and I
set
, an output channel is either:
in the CV mode if or in the CC mode if .
In the CV mode the output is a constant volta
e, so the current throu
h the load
depends on the load resistance (R
load
).
In the CC mode the output is a constant current, so the volta
e across the load
depends on the load resistance (R
load
).
The followin
picture shows when the output channel
oes into the CV or into the
CC mode of operation, when connected to a variable resistor R
load
.
If R
load
increases (R
load
> R
c
), the output channel
oes into the CV mode,
reducin
the current throu
h the load.
If R
load
decreases (R
load
< R
c
), the output channel
oes into the CC mode,
reducin
the volta
e across the load.
R
load
V
set
I
set
>
V
<
Rload >Rc
R=
∞ (open circuit)
Voltage
V(set)
Rc=
Vset
Iset
(crossover point)
Rload <Rc
CC
CV
I(set)
Current
ST5848
R=
0
(short circuit)
Fi
ure 5.5.7 Power Output Crossover Point
